1. Field of the Invention
The present process relates to the selective reaction of a trialkylaluminum compound with an organophosphorus dihalide to yield a halodiorganophosphine.
2. Description of the Prior Art
It is known to react trialkylaluminum compounds with phosphorus trichloride to yield various substitution products depending on the conditions used. See Chemical Abstracts, Vol. 53, 1122f (1959).
More recently, it has been disclosed that compounds of the formula RPCl.sub.2 (R being alkyl or aryl) can be alkylated with Grignard reagents (R'MgX) to form compounds of the formula RR'PCl. See Chemical Abstracts, Vol. 107, 77926s. However, the selectivity of these reactions is usually poor and mixtures result.
U.S. Pat. No. 3,036,132 to S. B. Becker has a general description of a metathesis reaction between (1) a phosphorus-halogen compound which is said to be of the formula PR.sub.n X.sub.3-n, where R can be a monovalent hydrocarbon radical and n can be 1 or 2 and (2) a compound of the formula AlR.sub.3 or M(AlR.sub.4).sub.n where R can be as described above, M can be alkali metal or alkaline earth metal, and n is the valence of M. This patent indicates that control of the ratio of equivalents of either reactant will control the extent of hydrocarbon substitution in the phosphorus compound. At Col. 4, lines 5-9, however, it indicates that its "specific examples" illustrate how "the reactions can be controlled to yield intermediate products of hydrocarbon substitution into the phosphorus-halogen reactants". The Examples contained in this patent only use lithium aluminum tetrapropyl with phosphorus trichloride. No examples or more specific disclosure using the less reactive trialkylaluminum and an organophosphorus dihalide are given. U.S. Pat. Nos. 3,974,217 to J. A. Miles (at Col. 1, lines 23-27) and 4,810,425 to G. E. Nelson (at Col. 1, lines 27-29) discuss the Becker '132 patent solely in terms of relating to use of the more reactive M(AlR.sub.4).sub.n compounds as a reagent with either phosphorus trichloride or phosphorus tribromide.